Representative patents showing some urethane formulations, and molding techniques for pneumatic tire formulations, are as follows:
U.S. Pat. No. 2,713,884 shows the manufacture of a tire composition having a tread section of polyester-diisocyanate elastomer bonded with an adhesive formulation of polyalkylene ether glycol diisocyanate elastomer to a rubber tire stock. The polyester diisocyanate elastomer was formed by reacting adipic acid with ethylene and propylene glycol and with 4,4'-methylene diphenyl diisocyanate.
U.S. Pat. No. 4,044,811 shows the manufacture of a laminated tire which utilizes a polyurethane formed from a prepolymer of toluene diisocyanate and a polyalkylene glycol such as poly(tetramethylene ether glycol) and a diamine chain extender such as ethylene diamine, methylene-bis(2-chloroaniline) (MOCA) and the like.
U.S. Pat. No. 4,090,547 shows the manufacture of a urethane tire wherein the urethane is formed by reacting a prepolymer of poly(tetramethylene ether glycol) and toluene diisocyanate having an isocyanate content of about 4% with meta-phenylenediamine as a chain extender. Similar formulations utilize MOCA as the chain extender.
In the manufacture of tires it has been customary to incorporate reinforcing cords into the tire to impart strength. Representative fibers as reinforcing cords for pneumatic tire applications are shown in U.S. Pat. Nos. 3,869,430; 3,977,172; 3,950,590; 3,929,180; 4,278,779; 4,044,540; 3,849,976; 3,826,298; 3,745,151; 3,690,363 and 4,155,394. Basically the common fibers utilized for reinforcing tires are glass filament, nylon, rayon, aromatic polyamides, polyvinyl alcohol, steel, polyethylene 2,6-naphthalate, and polyester. Within each class or family of tire cords compositions mentioned there are numerous modifications which are designed to achieve the desired characteristics in terms of strength, adhesion and other properties desired in tires.
One of the problems associated with the manufacture of reinforced polyurethane tires has been that the polyurethane resins were not able to withstand the heat generated at the point of contact with the reinforcing cord. It is known that the rapid compression and relaxation of the tire at the point of contact between the polyurethane composition and the cord causes heat buildup due to frictional forces. This heat must be dissipated otherwise the polymer will degrade and the tire will fail. Another problem, assuming the heat buildup problem was solved, has been one of obtaining desired tire strength. Numerous cords such as rayon, nylon and polyester when utilized in the manufacture of polyurethane tires generally do not provide this strength even though such fibers are effective in rubber bias and radial tires. As a partial explanation, polyurethane tires are made by casting a liquid medium into a mold and cured. The tires are not formed from belts as in rubber tire manufacture. When rayon and polyester cord are used as a reinforcing material, a substantial cord has to be utilized to achieve desired tire strengths. However, because there is a large amount of cord, it is difficult to achieve uniform dispersion of the urethane composition throughout the mass of reinforcing cord. As a result, good adhesion and contact is not achieved on a consistent basis. Other fibers, such as steel, although having desired strength, have poor adhesion to polyurethane compositions. Nylon has a tendency to elongate during molding.
U.S. Pat. Nos. 4,124,345; 4,277,295; and 4,259,129 relate to molding equipment for urethane tire manufacture and to reinforcing techniques for such tires.